Sheet feeder drive mechanism

ABSTRACT

A drive mechanism for controlling the separating and forwarding function of a sheet feeding device for imparting an asynchronous multi-directional motion to the sheet feeding mechanism for accomplishing reverse buckle feeding of individual sheets from a stack.

[ Nov. 20, 1973 United States Patent 1 Stemmle SHEET FEEDER DRIVEMECHANISM [75] Inventor:

.. 74/214 X 74/411 X 74/215 X 3,548,673 12/1970 Suchocki 3,496,791 21970 G b Denis J. Stemmle, Williamson, NY. 3 215 4 $1965 i Assignee:Xerox Corporation, Stamford,

Conn- Primary Examiner-Even C. Blunk [22] Filed; M 22, 1972 AssistantExaminer-James W. Miller Attorney-James J. Ralabate et a].

21 Appl. No.: 255,355

[57] ABSTRACT A drive mechanism for controlling the separating andforwarding function of a sheet feeding device for im- 271/22, 74/214,74/409 [51] Int. B65h 3/06, F1611 55/18 271/21, 22, 23;

[58] Field of Search..........................

parting an asynchronous multi-directional motion to the sheet feedingmechanism for accomplishing re- [56] References Cited UNITED STATESPATENTS 10/1909 Maegly verse buckle feeding of individual sheets from astack.

271/22 20 Claims, 4 Drawing Figures PATENTEURUY 2.0 1915 3,773,316

SHEET FEEDER DRIVE MECHANISM This invention relates generally to a drivemechanism and, in particular, to a drive mechanism for imparting anasynchronous multi directional motion to a sheet feeding mechanism.

More specifically, this invention relates to a paper feeding devicesuitable for use in an automatic reproducing machine, as for example, axerographic copier. In the xerographic copying art, a photosensitiveplate is initially charged uniformly in the dark and then exposed to alight image of original input scene information to be reproduced. Underthe influence of the light image, the charge on the plate is selectivelydissipated in the light struck regions so as to record the originalinput scene information in the form of a latent electrostatic image. Theplate is then developed by contacting the imaged areas with a tonermaterial specifically developed for this purpose wherein the toner iselectrically attracted into the imaged areas thereby rendering thelatent image visible. Finally, a sheet of final support material isplaced in overlying contact with the developed plate surface and thetoner image transferred from the plate surface to the final supportsheet. Generally, the sheets of support material are stored within themachine in a stack configuration and, upon demand, the sheets areindividually separated and forwarded from the stack into the transferstation.

One manner of achieving separation and forwarding of the individualsheets is by a technique known as reverse buckle" feeding. In thisparticular method, the rear margin of the stack is supported against therear wall of the sheet support tray so that the sheets are free to moveonly in a forward direction. Feeding means are then brought intooperative contact with the uppermost sheet in the stack and a motionimparted to the sheet to first drive the sheet rearwardly against therestraining force of the rear wall of the tray. As a consequence alongitudinal buckle is formed in the body of the sheet causing the sheetto be separated from the stack. Once separated, the direction of sheetmotion is reversed and the sheet advanced through the opening in thetray and cleared therefrom prior to instituting a subsequent feedingcycle.

Although reverse buckle feeding, as exemplifiedby the sheet feedingmechanism, disclosed in the US. Pat. No. 3,645,615 to Spear, representsa reliable method of separating and forwarding individual sheets from astack, it nevertheless has certain drawbacks which heretofore havelimited its use in the copying art. Ordinarily, a reverse buckle feederis driven by means of a pair of coacting gears which are programmed toimpart the desired motion to sheets during both the buckling andforwarding phases of each feeding cycle. Mating gear pairs generally areprovided with a certain amount of backlash to compensate for errors inthe generation of teeth, material expansion and to accommodatelubricants, dirt or the like. Backlash therefore is a broad termgenerally used to define the difference between the thickness of a geartooth and the width of the space in which it meshes.

As can be seen, backlash, when present, will allow one gear of a matingpair to be turned through some finite angle while the other gear remainsstationary. Where the gears are adapted to drive in a single directionunder uniform loading conditions, the effects of backlash are more orless minimized. However, where the drive is forced to periodicallychange direction under varying loads, as in the case of a conventionalreverse buckle feeder drive, the effects can be serious. It has beenfound,'for example, when standard gears are used in the feedingapparatus disclosed in the previously noted Spear disclosure, severetorque spikes are generated which are ultimately broadcast throughoutthe machine. These forces can be of a magnitude sufficient to disturbthe sensitive optics" involved resulting in the production of degradedcopy. I i

It is therefore an object of the present invention to improve apparatusfor separating and forwarding individual sheets from a stack.

It is a further object of the present invention to provide a drivemechanism for a reverse buckle sheet feeding apparatus.

A still further object of this invention is to minimize the generationof unwanted forces in a copying machine during the processing of copysheets.

A yet further object of the present invention is to provide a positivedrive that is free of backlash.

These and other objects of the present invention are attained by meansof a sheet feeding drive having an elastomeric direct contact elementarranged to drive a sheet feeding mechanism and at least one motionimparting device having a profile working surface thereon adapted tomove in friction drive contact with the elastomeric element whereby apredetermined motion is translated through the. elastomeric element fromthe motion imparting device to the sheet feeding mechanism.

For a better understanding of the present invention as well as otherobjects and further features thereof, reference is had to the followingdetailed description of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic view illustrating an automatic xerographic machineembodying the present invention;

FIG. 2 is a perspective view of a paper feeding device embodying thedrive mechanism of the present invention;

FIG. 3 is a partial end view showing the drive mechanism of the presentinvention imparting a rearward mo tion to the upper most sheet in astack to form a separating buckle therein; and

FIG. 4 represents a partial end view of the drive mechanism of thepresent invention showing the drive mechanism imparting a sheetadvancing motion to the separated sheet.

Referring now to the drawings, there is shown for the purposesofexplanation an automatic xerographic re producing machine incorporatingthe improved sheet feeding mechanism of the present invention. Thecopying machine illustrated in FIG. 1 employs an image recordingdrum-like member 5, the outer periphery of which is coated with asuitable photoconductive material 6 that is well known and used in theart for recording a latent electrostatic image of an original to bereproduced. Drum 5, which is suitably joumaled for rotation within amachine frame by means of a shaft 7, rotates in the direction indicatedto bring the image retaining surface thereon past a plurality ofxerographic processing stations. Suitable drive means (not shown) isprovided to power and coordinate the motion of the various cooperatingmachine components whereby a faithful reproduction of the original inputscene information is recorded upon a sheet of final support materialsuchas paper or the like.

Since the practice of xerography is well known in the art, the variousprocessing stations for producing a copy of an original are hereinrepresented in FIG. 1 as blocks A-E. At station A, an electrostaticcharge is placed uniformly over the photoconductive surface of the drumpreparatory to imaging. The charged drum surface is then passed throughan exposure station B for illuminating at least a portion of the chargesurface with a light image of the original input scene informationwhereby the charge is selectively dissipated in the light exposedregions to record the original input scene in the form of a latentelectrostatic image. Next, in the direction of drum rotation, the imagebearing plate surface is transported through a developing station Cwherein toner material is applied to the surfaceof the image bearingplate rendering the latent image visible. The developed image is thenbrought into contact with a sheet of final support material 8, such aspaper or the like, within a transfer station D and the toner imagetransferred from the plate surface to the contacting side of the finalsupport sheet. Finally, at cleaning station E, residual toner particles,remaining on the drum surface after the transfer operation, are removedfrom the drum in a manner well known in the art thus placing thephotoconductive surface in a condition to be reused in the xerographicrecording process.

It is herein comtemplatedthat the sheets of final support materialprocessed in the automatic xerographic reproducing device will be storedin the machine within a removable paper cassette 10. It is furthercontemplated that the automatic reproducing machine will have thecapability of accepting and processing copy sheets of varying lengths,the length of the copy sheet, of course, being dictated by the size ofthe original input scene information recorded on the photoconductor. Tothis end, the paper cassette is provided with an adjustable featurewhereby sheets of varying'lengths can be conveniently accommodatedtherein. In operation, the cassette is filled with a stack of paper ofpreselected size and the cassette inserted into the machine by slidingthe cassette along a base plate which guides the cassette into operablerelationship with a pair of feed rollers 12. When properly positioned inoperable communication with the feed rollers, the top most sheet in thestack is separated and forwarded from the stack into the transferstation in a manner to be described in greater detail below.

Referring now more specifically to FIG. 2, there is illustrated a sheetfeeding device for separating and forwarding individual sheets of finalsupport material from a supply stack into the subsequent sheet handlingand- /or processing equipment. The sheets are stored in a stackconfiguration, generally referred to as 15, within the supply cassette10. The stack is supported upon a generally horizontal platform 13 withthe rear margin of the stack positioned in abutment against the rearwall retaining elements 14 of the supply tray. The front end of the.supply tray, through which the sheets are forwarded, is provided with anopening with the front or leading edge of the stack being restrained inthe tray by means of a pair of retaining tabs 17, one of which beingclearly illustrated in FIG. 2.

Normally, the restraining tabs rest in overlying contact with theuppermost sheet in the stack and serve to hold the front margin of thestack in alignment during the sheet separating and advancingprocessifhepair of sheet feed rollers 12 which are mounted above the supply trayupona rotatable drive shaft :18 are arranged to operatively communicatein friction driving contact with-the uppermostsheet of the stack-a::"I-Fhe v feed roll members are made of a material,1such..as rubber orthe like, havinga highcoefi'icient oflfriction to minimize slippagebetween the :rollers andrthe :sheet'in process during the sheet-feedingcycle. 7 f

i The particular sheet separating 'andfeeding operation herein employedis commonly referred to as -reverse buckle feeding. This sheetgfeedingtechnique will be explained in further detail with specific reference toFIGS. 1 and 2. To accomplish this type' of sheet feeding, the feedrollers are rotatably mounted in stationary position above the stack andthe, supply cassette rocked about a pivot 20 located nearthe rear marginof the tray causing the uppermost sheet in the stack to be moved intoand out of operative contact with the rotatably mounted feed rollers. Aspring member 22,is positioned below the supply tray and is arranged toact upon the bottom wall 13 thereof so as to continually bias the tray,and consequently the stacks supported therein, upwardly towards thefixedly positioned feed rollers.

The movement of the tray is coordinated with the movement of the feedrollers through the paper feed drive system which includes a timing belt(FIG. 2) driven in the direction indicated by means of a power inputshaft 27 and a drive pulley 28. The timing belt is tracked about pulleys30 and 31 which serve to provide power to the sheet'separating andforwarding drive mechanism 34 and the sheet registering and advancingdrive mechanism 35, respectively.

Pulley 31 is co-axially aligned with a pair of contoured cams 37 and 38upon a stub shaft 40 which is journaled for rotation in the main machineframe (not shown). Each front margin retaining tab 17 is connected viaarm 41, rocker shaft 42 and by a cam follower 43 with the workingsurface of the control cam 37. The motion imparted to the tabs throughthe cooperating mechanism is programmed to move the paper cassetteupwardly under the urging of spring 22 at the start of each feedingcycle whereby the uppermost sheet in the stack is positioned in frictioncontact with the feed rollers. For further information concerning thistype of apparatus reference is had to a pending application Ser. No.205,91 I filed in the name of Punnett et al.

At the start of each sheet feeding cycle, the feed rollers are placed incontact with the uppermost sheet in the stack and the rollers are drivenin the direction illustrated in FIG. 3 causing the uppermost sheet inthe stack to be moved rearwardly against the restraining influence ofthe supply tray rear wall members 14. The top sheet 29 is moved backsufficiently to free the leading edge thereof from beneath the tabelements 17. As a consequence,-a longitudinal buckle, as shown in FIG.3, is formed in the trailing portion of the sheet thus separating thesheet from the remainder of the supply stack. Once separated, thedirection of rotation of the feed rollers is reversed (FIG. 4) and thesheet then forwarded over the retaining tabs a sufi'lcient distance toplace the leading edge of the sheet between a pair of cooperating pinchrollers and 51 positioned adjacent to the open end of the supplycassette. The bottom roller 51 of the pinch roller arrangement iscontinually driven in the direction indicated by means of an input shaft53 while the upper roll 50 is periodically moved in and out of contactwith the lower roll to facilitate the forwarding of a separated sheettherebetween.

The action of the upper roll is regulated by means of 5 the secondcontrol cam 38 affixed to shaft 40. The support shaft 52, upon whichroller 50 is mounted, is secured at one end in a pivoted link 54 and thelink, in turn, is pivoted in a second link 56 which is held in operativecommunication with cam follower 55 through a connecting shaft 57.

Initially, at the beginning of a sheet feeding cycle, cam 38 serves tohold the upper roller 50 in a raised position as illustrated in FIG. 4thus allowing the leading edge of a sheet forwarded from the supplystack to pass freely between the two cooperating pinch rollers. Asexplained in greater detail in the previously mentioned Punnett et aldisclosure, the leading edge of the sheet is driven between the pinchrollers into a registration gate (not shown) to properly align andregister the sheet with the subsequent sheet processing station. Whenthe sheet has reached the proper position beneath the pinch rollers,-thecam follower 55 and the associated linkage mechanism imparts a motion tothe shaft 52 causing the upper roller to move downwardly locking thesheet in friction driving contact between the two roller members.Simultaneously therewith, the first cam, that is, cam 37, translates amotion to the retaining tabs 17 causing the tabs to pull the traydownwardly away from feed rollers 12 freeing the sheet in the sheetadvancing function is taken over by the pinch rollers which advance thesheet into the station D (FIG. 1) and the developed image recorded onthe drum placed on the copy sheet.

Ordinarly when a single pair of cooperating gear elements are reliedupon to translate the entire motion sequence to the feed rollers, as forexample the drive disclosed in the aforementioned Punnett et aldisclosure, the backlash between the coacting gears causes unwantedtorque spikes to be generated particularly at the time of motion changewhich occurs during the transition period between the reverse bucklephase and the forwarding phase of each feeding cycle. The driveapparatus of the present invention, because of its uniquecharacteristics, minimizes the effect of backlash in the system andtranslates a smooth input to the feed rollers throughoutall phases ofthe sheet feeding cycle and, in efiect eliminates the generation ofunwanted forces within the machine.

As illustrated in FIGS. 2-4, the drive system of the present inventioninvolves a concentric elastomeric roller 60 arranged to cooperate withtwo motion imparting elements, a first reverse buckling element 62 and asecond sheet forwarding element 63. The elastomeric roller is rigidlyaffixed to the outboard end of the feed roller drive shaft 18 asillustrated clearly in FIG. 2. The two motion imparting elements 62 and63 are rotatably mounted upon stub shafts 72 and 73, respectively andthe shafts fixed in the side wall of the machine frame. The stub shaftsare positioned in relation to the feed roller drive shaft so that theworking profiles of the motion imparting elements move in and out ofdriving contact with the outer periphery of the elastomeric roller asthe elements are rotated in the directions indicated.

The two segmented motion imparting elements 62, 63 are fabricated of ametal material such as aluminum process from the remainder of the stack.At this time,

or the like. The contacting peripheries of each of the motion impartingelements as well as the outer periphery of the elastomeric roller areprovided with a textured or grooved working surface to enhance thedriving characteristics between the contacting elements.

In practice, the elastomeric roll member and the segmented motionimparting drive elements are something more than just conventionalfriction drive elements in that they cooperate to provide a system inwhich slippage is minimized and backlash, for all practical purposes, iseliminated. To obtain this truly unique result, the resilientelastomeric roll is contructed of a polyurethane material having ahardness of between 20 and durometers and provided with a series ofuniformly spaced longitudinally extending grooves about the outersurface thereof. The grooves preferably are V- shaped in constructionwith the side walls meeting to form an included angle of approximatelyThe circular pitch between grooves is sufficient to provide a top landof about 0.006 inches between each groove. The segmented working surfaceof each drive element is formed of a relatively non-deformable material.The working surface of the drive elements are also provided withlongitudinally extending V-shaped grooves. These grooves, however, areotherwise quite dissimilar in construction to those formed in theelastomeric roll. Preferably, these grooves are shaped so that the sidewalls form an included angle of about 60. The tooth spacing found on theurethane roll is dissimilar from that found on the drive elements withthe circular tooth pitch on one of the coacting members being somenon-integer multiple of the circular tooth pitch found on the other.

Although the profile created on each of the coacting members aretooth-like in appearance, they are nevertheless not gear-like inconstruction. The grooves are designed so that both the circular pitchand the tooth profile found on the urethane roll member differs fromthat on the segmented drive elements. As a result, during a paperfeeding cycle, some of the teeth involved may tend to mesh with eachother in a gear-like manner while other teeth on the driving elementwill be forced into deforming contact against the lands or other partsor the urethane roll surface. However, because of the uniqueconstruction involved, all the teeth on the drive elements will in somemanner depress the urethane roller whether they contact at the peak orvalleys and thus provide a positive non-slip driving action throughoutevery phase of the paper feeding cycle.

Affixed to the motion imparting elements 62 and 63 are a pair ofcooperating (meshing) spur gears 74 and 75 through which the drivingpower from the main drive system is transmitted to the motion impartingelements. A drive pulley 30, which is part of the main drive system, isoperatively connected to gear 74 and operates to cause the gear tocontinually drive in one direction, (counter clockwise as shown in FIG.2), in predetermined timed relation with the other operating machinecomponents. Gear 74, in turn, meshes with gear 75 and continually drivesthe coacting gear in the opposite direction.

The camming action of the pinch rollers 50 and 51 as well as the othermachine functions, is coordinated with the mou'on of the feed rollers 12through the timing belt and pulley arrangement whereby a sheet of finalsupport material arrives at the transfer station in movingsynchronization with the developed xerographic image recorded on thephotoconductive drum surface.

At the beginning of each paper feeding cycle, the smaller of the twosegmented motion imparting elements, the reverse buckle elements 62, isrotated into pressure driving contact with the outer periphery of theelastomeric roller 60. As illustrated in FIG. 3, the reverse buckleelement 62 imparts a prescribed motion to the feed rollers which causesthe uppermost sheet in the stack to be moved rearwardly towards the backof the supply cassette. The rear margin of the sheet, however, isrestrained by the rear wall of the cassette whereby a longitudinalbuckle is formed along the body of the sheet thus separating the sheetfrom the remaintier of the stack. The leading edge of the separatedsheet is moved back sufficiently to effect the release of the sheet frombeneath the front edge'retaining tabs 17. As the meshing spur gearelements 74 and 75 continue to drive in the direction indicated, theworking surface of the reverse buckle elements 62 moves out of contactwith the elastomeric roller 60 terminating the reverse buckle phase ofthe sheet feeding cycle. At this time, without reversing the directionof rotation of the spur gear elements, the second forward feedingelement 63 is moved into pressure contact with the elastomeric rollercausing a reversal in the direction of the sheet feeding-rollers l2 andinstituting the sheet forwarding phase of the sheet feeding cycle. Asshown in FIG. 4, the sheet advancing phase of the sheet feeding cyclebegins as element 63 drives the elastomeric element 60 in a counterclockwise direction causing the separated sheet to be advanced by thefeed rollers over the top of the retaining tabs whereby the sheet ispresented between the cooperating pinch rollers 50, 51.

As explained above, the control cam 38 causes the rated and forwardedsheet. Simultaneously therewith,

control cam 38 brings cooperating pinch rollers 50 and 51 into frictiondriving contact with the" sheet in process driving the freed sheet intothe sheet transfer station D, (FIG. 1). Sufficient dwell time isprovided within the control cam system to allow the trailing edge of thesheet in process to be cleared from beneath speed rollers 12 before thenext feeding cycle is commenced. As can be seen, because the uniquecharacteristics of the present system, the spur gear elements whichprovide the drive to the paper feeder continually rotate in a singledirection thereby minimizing the effect of backlash. Furthermore, itshould be noted that the drive system herein disclosed is directlyconnected to the main drive system'thereby eliminating the need forclutches or the like.

While thisinvention has been described with reference to the structuredisclosed herein, it is not necessarily confined to the details as setforth and this application is intended to cover such modifications andchanges as may come within the scope of the following claims.

I claim:

1. A drive mechanism including:

a deformable cylindrical member having a series of unifonnly spacedlongitudinal grooves provided about the periphery thereof with thegrooves being at a first circular pitch,

a relatively non-deformable drive member having a working surfacethereon arranged to move into and out of pressure contact against theouter periphery of said cylindrical member, said working surface havinga series of uniformly spaced grooves formed therein at a second circularpitch different from said first circular pitch so that some ofthe areabetween the grooves on said drive member act to deform the surface ofsaid cylindrical member in pressure contact therewith and other areas between said grooves meshes with the grooves formed in said cylindricalmember whereby a positive drive that is free of backlash is maintainedbetween the two coacting members.

2. The drive system as described in claim .1 having a plurality of drivemembers being arranged so that the working surfaces thereon sequentiallymove into and out of pressure driving contact with said cylindricalmember.

3. The apparatus of claim 1 wherein the grooves formed in thecylindrical member are V-shaped having an included angle of aboutbetween the side walls thereof and the grooves formed in said drivemember is V-shaped having an included angle of about 60 between the sidewalls thereof.

4. The apparatus of claim I, wherein said cylindrical member is formedof a urethane material.

5. The drive mechanism of claim 1 wherein the areas between grooves onthe drive member deforms the surface of the deformable member in boththe peak and valley regions thereon when said drive member is moved incontact with the deformable member to insure a positive drive.

6. An apparatus for driving a sheet feeding mechanism comprising:

sheet feeding means for advancing individual sheets from a supply stack;

a resilient elastomeric roll member in operative communication with saidsheet feeding means, whereby motion imparted to said roll member istranslated to the individual sheet, said roll member having a series ofspaced longitudinally extending grooves provided about the peripherythereof, said grooves having a first circular pitch;

at least one motion imparting element having a working surface thereonarranged to move in frictional driving contact against the periphery ofsaid roll member, whereby a prescribed motion is translated from said atleast one element to said roll member, said working surface having aseries of spaced longitudinally extending grooves therein, said groovesin said working surface having a second circular pitch different fromsaid first circular pitch.

7. An apparatus as in claim 6 wherein, said at least one element isrelatively non-deformable.

8. An apparatus as in claim 6 wherein, the periphery of said roll memberand the working surface of said at least one element are tooth-like,with the tooth profile on said roll member being different from thetooth protile on said at least one element.

9. An apparatus as in claim 6 wherein, said first tooth pitch is anon-interger multiple of said second tooth pitch.

10. An apparatus as in claim 6 including a plurality of motion impartingelements arranged so that the working surfaces thereon sequentially moveinto and out of frictional driving contact with said roll member.

11. An apparatus as in claim 10 wherein, first and second motionimparting elements are provided, said most sheet in said stack, saidfeed roll being supported by a shaft connected to said roll member,whereby said first motion imparting element causes said feed roller toadvance the uppermost sheet rearwardly against the rear wall of saidsupply tray to form a separating buckle therein and said second motionimparting element causes said feed roll to reverse the direction inwhich said sheet is being advanced so as to forward said sheet from saidsupply tray.

13. An apparatus as in claim 12, wherein said feed roll and said rollmember are coaxially supported upon said shaft.

14. An apparatus as in claim 13, wherein a gear is operatively connectedto each of said first and second elements said gears being meshedtogether to coordinate the motion of said first and second elements.

15. An apparatus as in claim 10, wherein a gear is operatively connectedto each of said elements and wherein said gears are meshed together tocoordinate the motion of said elements.

16. An apparatus as in claim 14, wherein said elements are formed of arelatively non-deformable material.

17. An apparatus as in claim 16, wherein the periphery of said rollmember and the working surfaces of said elements are tooth-like with thetooth profile on said roll member being different from the tooth profileon said elements.

18. An apparatus as in claim 17, wherein the grooves formed in theperiphery of said roll member are V- shaped having an included angle ofabout between the sidewalls thereof and the grooves formed in saidelements are V-shaped having an included angle of about 60 between thesidewalls thereof.

19. An apparatus as in claim 18, wherein said roll member is formed of aurethane material.

20. An apparatus as in claim 19, wherein said elements are formed ofaluminum.

1. A drive mechanism including: a deformable cylindrical member having aseries of uniformly spaced longitudinal grooves provided about theperiphery thereof with the grooves being at a first circular pitch, arelatively non-deformable drive member having a working surface thereonarranged to move into and out of pressure contact against the outerperiphery of said cylindrical member, said working surface having aseries of uniformly spaced grooves formed therein at a second circularpitch different from said first circular pitch so that some of the areabetween the grooves on said drive member act to deform the surface ofsaid cylindrical member in pressure contact therewith and other areasbetween said grooves meshes with the grooves formed in said cylindricalmember whereby a positive drive that is free of backlash is maintainedbetween the two coacting members.
 2. The drive system as described inclaim 1 having a plurality of drive members being arranged so that theworking surfaces thereon sequentially move into and out of pressuredriving contact with said cylindrical member.
 3. The apparatus of claim1 wherein the grooves formed in the cylindrical member are V-shapedhaving an included angle of about 90* between the side walls thereof andthe grooves formed in said drive member is V-shaped having an includedangle of about 60* between the side walls thereof.
 4. The apparatus ofclaim 1, wherein said cylindrical member is formed of a urethanematerial.
 5. The drive mechanism of claim 1 wherein the areas betweengrooves on the drive member deforms the surface of the deformable memberin both the peak and valley regions thereon when said drive member ismoved in contact with the deformable member to insure a positive drive.6. An apparatus for driving a sheet feeding mechanism comprising: sheetfeeding means for advancing individual sheets from a supply stack; aresilient elastomeric roll member in operative communication with saidsheet feeding means, whereby motion imparted to said roll member istranslated to the individual sheet, said roll member having a series ofspaced longitudinally extending grooves provided about the peripherythereof, said grooves having a first circular pitch; at least one motionimparting element having a working surface thereon arranged to move infrictional driving contact against the periphery of said roll member,whereby a prescribed motion is translated from said at least one elementto said roll member, said working surface having a series of spacedlongitudinally extending grooves therein, said grooves in said workingsurface having a second circular pitch different from said firstcircular pitch.
 7. An apparatus as in claim 6 wherein, said at least oneelement is relatively non-deformable.
 8. An apparatus as in claim 6wherein, the periphery of said roll member and the working surface ofsaid at least one element are tooth-like, with the tooth profile on saidroll member being different from the tooth profile on said at least oneelement.
 9. An apparatus as in claim 6 wherein, said first tooth pitchis a non-interger multiple of said second tooth pitch.
 10. An apparatusas in claim 6 including a plurality of motion imparting elementsarranged so that the working surfaces thereon sequentially move into andout of frictional driving contact with said roll member.
 11. Anapparatus as in claim 10 wherein, first and second motion impartingelements are provided, said first motion imparting element beingarranged to move in a first direction and said second motion impartingelement being arranged to move in an opposite direction.
 12. Anapparatus as in claim 11, wherein said sheet feeding means includes asupply tray for supporting said stack, a feed roll arranged to contactthe uppermost sheet in said stack, said feed roll being supported by ashaft connected to said roll member, whereby said first motion impartingelement causes said feed roller to advance the uppermost sheetrearwardly against the rear wall of said supply tray to form aseparating buckle therein and said second motion imparting elementcauses said feed roll to reverse the direction in which said sheet isbeing advanced so as to forward said sheet from said supply tray.
 13. Anapparatus as in claim 12, wherein said feed roll and said roll memberare coaxially supported upon said shaft.
 14. An apparatus as in claim13, wherein a gear is operatively connected to each of said first andsecond elements said gears being meshed together to coordinate themotion of said first and second elements.
 15. An apparatus as in claim10, wherein a gear is operatively connected to each of said elements andwherein said gears are meshed together to coordinate the motion of saidelements.
 16. An apparatus as in claim 14, wherein said elements areformed of a relatively non-deformable material.
 17. An apparatus as inclaim 16, wherein the periphery of said roll member and the workingsurfaces of said elements are tooth-like with the tooth profile on saidroll member being different from the tooth profile on said elements. 18.An apparatus as in claim 17, wherein the grooves formed in the peripheryof said roll member are V-shaped having an included angle of about 90*between the sidewalls thereof and the grooves formed in said elementsare V-shaped having an included angle of about 60* between the sidewallsthereof.
 19. An apparatus as in claim 18, wherein said roll member isformed of a urethane material.
 20. An apparatus as in claim 19, whereinsaid elements are formed of aluminum.